<?php
    /**
     * Class: Route
     * Handles the routing process and other route-related tasks.
     */
    class Route {
        # String: $action
        # The current action.
        public $action = "";

        # String: $request
        # The extracted request.
        public $request = "";

        # Array: $arg
        # Clean URLs decomposed into an array of arguments.
        public $arg = array();

        # Array: $try
        # An array of actions to try until one doesn't return false.
        public $try = array();

        # Boolean: $ajax
        # Shortcut to the AJAX constant (useful for Twig).
        public $ajax = AJAX;

        # Boolean: $success
        # Did <Route.init> call a successful route?
        public $success = false;

        # Variable: $controller
        # The Route's Controller.
        public $controller;

        /**
         * Function: __construct
         * Parse the URL and give the controller an opportunity to determine the action.
         *
         * Parameters:
         *     $controller - The controller to use.
         */
        private function __construct($controller) {
            if (!in_array("Controller", class_implements($controller)))
                trigger_error(
                    __("Route was initiated with an invalid Controller."),
                    E_USER_ERROR
                );

            $config = Config::current();

            fallback($controller->feed, isset($_GET['feed']));

            # Set the contoller for this route.
            $this->controller = $controller;

            # Determining the action can be this simple if clean URLs are disabled.
            $this->action =& $_GET['action'];

            $base = ($controller->base == "") ?
                $config->url :
                $config->chyrp_url."/".$controller->base ;

            $regex = "~^".preg_quote(
                oneof(parse_url($base, PHP_URL_PATH), ""),
                "~"
            )."((/)index.php)?~";

            # Extract the request.
            $this->request = preg_replace($regex, '$2', $_SERVER['REQUEST_URI']);

            # Decompose clean URLs.
            $this->arg = array_map(
                "urldecode",
                explode("/", trim($this->request, "/"))
            );

            # Give the controller an opportunity to parse this route
            # and determine the action.
            $controller->parse($this);

            Trigger::current()->call("parse_route", $this);

            # Support single parameter actions without custom routes
            # or parsing by the controller.
            if (empty($this->action)) {
                if (
                    !empty($this->arg[0]) and
                    !preg_match("/[\W]/", $this->arg[0])
                )
                    $this->try[] = $this->arg[0];
            }
        }

        /**
         * Function: init
         * Attempt to call a responder until one of them doesn't return false.
         */
        public function init(): bool {
            $trigger = Trigger::current();
            $visitor = Visitor::current();

            $trigger->call("route_init", $this);

            if (isset($this->action))
                array_unshift($this->try, $this->action);

            foreach ($this->try as $key => $val) {
                list($method, $args) = is_numeric($key) ?
                    array($val, array()) :
                    array($key, $val) ;

                $this->action = $method;

                # Don't try to call anything except a valid PHP function.
                if (preg_match("/[\W]/", $this->action))
                    error(
                        __("Error"),
                        __("Invalid action."),
                        code:400
                    );

                # Return 403 if the visitor cannot view the site
                # and this is not an exempt action.
                if (
                    !$visitor->group->can("view_site") and
                    !$this->controller->exempt($this->action)
                ) {
                    $trigger->call("can_not_view_site");
                    show_403(
                        __("Access Denied"),
                        __("You are not allowed to view this site.")
                    );
                }

                $name = strtolower(
                    str_replace(
                        "Controller",
                        "",
                        get_class($this->controller)
                    )
                );

                # This discovers responders provided by extensions.
                if (
                    $trigger->exists($name."_".$method) or
                    $trigger->exists("route_".$method)
                ) {
                    $call = $trigger->call(
                        array($name."_".$method, "route_".$method),
                        $this->controller
                    );
                } else {
                    $call = false;
                }

                if ($call !== false) {
                    $this->success = true;
                    break;
                }

                # This discovers responders native to the controller.
                if (method_exists($this->controller, $name."_".$method)) {
                    $response = call_user_func_array(
                        array($this->controller, $name."_".$method),
                        $args
                    );
                } else {
                    $response = false;
                }

                if ($response !== false) {
                    $this->success = true;
                    break;
                }
            }

            # Return 404 if routing failed and nothing was displayed.
            if (!$this->success and !$this->controller->displayed)
                show_404();

            # Set redirect_to for actions that visitors
            # might want to return to after they log in.
            if (
                $this->controller->displayed and
                !$this->controller->feed and
                !$this->controller->exempt($this->action) and
                empty($_POST)
            ) {
                $_SESSION['redirect_to'] = self_url();
            }

            $trigger->call("route_done", $this);

            return $this->success;
        }

        /**
         * Function: url
         * Constructs an absolute URL from a relative one. Converts clean URLs to dirty.
         *
         * Parameters:
         *     $url - The relative URL. Assumed to be dirty if it begins with "/".
         *     $controller - The controller to use. Current controller used if omitted.
         *
         * Returns:
         *     An absolute clean or dirty URL, depending on value of @Config->clean_urls@
         *     and @controller->clean_urls@.
         */
        public static function url($url, $controller = null): string {
            $config = Config::current();

            if (!isset($controller))
                $controller = Route::current()->controller;

            if (is_string($controller))
                $controller = $controller::current();

            $base = ($controller->base == "") ?
                $config->url :
                $config->chyrp_url."/".$controller->base ;

            # Assume this is a dirty URL and return it without translation.
            if (str_starts_with($url, "/"))
                return fix($base.$url, true);

            # Assume this is a clean URL and ensure it ends with a slash.
            $url = rtrim($url, "/")."/";

            # Translation is unnecessary if clean URLs are enabled
            # and the controller supports them.
            if ($config->clean_urls and $controller->clean_urls)
                return fix($base."/".$url, true);

            $urls = $controller->urls;

            Trigger::current()->filter($urls, "parse_urls");

            # Generate a feed variant of all dirty translations
            # not native to the controller.
            foreach (
                array_diff_assoc($urls, $controller->urls) as $key => $value
            ) {
                $delimiter = substr($key, 0, 1);
                $index = substr($key, 0, -1).
                         preg_quote("feed/", $delimiter).
                         $delimiter;

                $urls[$index] = $value."&amp;feed";
            }

            # Add a fallback for single parameter translations.
            $urls['|/([^/]+)/$|'] = '/?action=$1';

            # Do the translation.
            $translation = preg_replace(
                array_keys($urls),
                array_values($urls),
                "/".$url,
                1
            );

            return fix($base.$translation, true);
        }

        /**
         * Function: add
         * Adds a route to the blog.
         *
         * Parameters:
         *     $path - The path to add. Wrap variables with () e.g. "tag/(name)/".
         *     $action - The action. Add parameters with ; e.g "tag;foo=bar;baz=boo".
         *
         * Notes:
         *     Required for actions that have more than one parameter.
         *     For example, not needed for /tags/ but needed for /tag/(name)/.
         *
         * See Also:
         *     <remove>
         */
        public function add($path, $action): void {
            $config = Config::current();
            $new_routes = $config->routes;
            $new_routes[$path] = $action;
            $config->set("routes", $new_routes);
        }

        /**
         * Function: remove
         * Removes a route added by <add>.
         *
         * Parameters:
         *     $path - The path to remove.
         *
         * See Also:
         *     <add>
         */
        public function remove($path): void {
            $config = Config::current();
            $new_routes = $config->routes;
            unset($new_routes[$path]);
            $config->set("routes", $new_routes);
        }

        /**
         * Function: custom
         * Parses custom routes stored in the configuration.
         *
         * Notes:
         *     The / path strictly requires no request args.
         */
        public function custom(): void {
            if (!$this->controller instanceof MainController)
                return;

            $config = Config::current();

            foreach ($config->routes as $path => $action) {
                preg_match_all("/\(([^\)]+)\)/", $path, $variables);

                $exp = ($path == "/") ?
                        "\$" :
                        preg_replace(
                            "/\\\\\(([^\)]+)\\\\\)/",
                            "([^\/]+)",
                            preg_quote(oneof(trim($path, "/"), "/"), "/")
                        ) ;

                # Expression matches?
                if (preg_match("/^\/{$exp}/", $this->request, $args)) {
                    array_shift($args);

                    # Populate $_GET variables discovered in the path.
                    if (isset($variables[1])) {
                        foreach ($variables[1] as $index => $variable)
                            $_GET[$variable] = urldecode($args[$index]);
                    }

                    # Populate $_GET variables contained in the action.
                    $params = explode(";", $action);
                    $action = $params[0];

                    array_shift($params);

                    foreach ($params as $param) {
                        $split = explode("=", $param);
                        fallback($split[1], "");
                        $_GET[$split[0]] = urldecode($split[1]);
                    }

                    # Set the action.
                    $this->action = $action;
                }
            }
        }

        /**
         * Function: current
         * Returns a singleton reference to the current class.
         */
        public static function & current($controller = null): ?self {
            static $instance = null;

            if (!isset($controller) and empty($instance))
                return $instance;

            $instance = (empty($instance)) ? new self($controller) : $instance ;
            return $instance;
        }
    }